UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net income	$ 329,270	$ 154,254
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	260,560	215,206
Allowance for doubtful accounts	6,684	7,186
Amortization of deferred financing costs and debt discount	4,734	2,718
Accretion of environmental liabilities	9,599	8,625
Changes in environmental liability estimates	2,105	341
Deferred income taxes	2,226	5,202
Other (income) expense, net	(2,073)	2,509
Stock-based compensation	20,375	12,786
Gain on sale of business	(8,864)	0
Environmental expenditures	(9,720)	(12,223)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(293,562)	(113,601)
Inventories and supplies	(44,324)	(12,882)
Other current and non-current assets	(12,600)	(10,785)
Accounts payable	52,979	86,974
Other current and long-term liabilities	40,153	21,916
Net cash from operating activities	357,542	368,226
Cash flows used in investing activities:
Additions to property, plant and equipment	(244,547)	(146,654)
Proceeds from sale and disposal of fixed assets	5,118	16,424
Acquisitions, net of cash acquired	(73,568)	(22,819)
Proceeds from sale of business, net of transaction costs	16,811	0
Additions to intangible assets including costs to obtain or renew permits	(1,094)	(2,659)
Proceeds from sale of available-for-sale securities	51,736	83,226
Purchases of available-for-sale securities	(36,418)	(96,785)
Net cash used in investing activities	(281,962)	(169,267)
Cash flows used in financing activities:
Change in uncashed checks	887	(4,323)
Tax payments related to withholdings on vested restricted stock	(6,214)	(7,383)
Repurchases of common stock	(44,182)	(48,409)
Deferred financing costs paid	(410)	(150)
Payments on finance leases	(9,538)	(5,845)
Principal payments on debt	(13,152)	(5,652)
Net cash used in financing activities	(72,609)	(71,762)
Effect of exchange rate change on cash	(6,523)	365
(Decrease) increase in cash and cash equivalents	(3,552)	127,562
Cash and cash equivalents, beginning of period	452,575	519,101
Cash and cash equivalents, end of period	449,023	646,663
Cash payments for interest and income taxes:
Interest paid	86,407	61,807
Income taxes paid, net of refunds	53,183	48,202
Non-cash investing activities:
Property, plant and equipment accrued	23,726	11,561
Remedial liability assumed in acquisition of property, plant and equipment	8,092	0
ROU assets obtained in exchange for operating lease liabilities	39,899	18,528
ROU assets obtained in exchange for finance lease liabilities	$ 11,263	$ 18,704